Charging in communication networks

ABSTRACT

This invention relates to a method for supporting a communication session of an user equipment, by means of a communication system that includes at least one entity between the user equipment and a node with which the user equipment is arranged to establish a session, the method including the steps of establishing a session between the user equipment and the node via the at least one entity, putting the session on hold, reserving resources for the session while the session is on hold, and resuming the session and distributing charging information.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present specification relates generally to charging incommunication networks. The present specification also relatesgenerally, but not exclusively, to third generation (Universal MobileTelecommunication System UMTS) networks.

[0003] 2. Description of the Related Art

[0004] A communication system generally refers to a facility thatenables communication between two or more entities such as user terminalequipment and/or network entities and other nodes associated with acommunication system. The communication may comprise, for example,communication of voice, electronic mail (email), text messages, data,multimedia and so on.

[0005] The communication may be provided by a fixed line and/or wirelesscommunication interfaces. A feature of some wireless communicationsystems is that they provide mobility for the users thereof. An exampleof communication systems providing wireless communication is a publicland mobile network (PLMN). An example of the fixed line system is apublic switched telephone network (PSTN).

[0006] A communication system typically operates in accordance with agiven standard or specification which sets out what the various elementsof a system are permitted to do and how that should be achieved. Forexample, the standard or specification may define if the user, or moreprecisely user equipment, is provided with a circuit switched server ora packet switched server or both. Communication protocols and/orparameters which are preferably used for the connection are alsotypically defined. For example, the manner of how communication shall beimplemented between the user equipment and the elements of thecommunication networks is typically based on a predefined communicationprotocol. In other words, a specific set of “rules” on which thecommunication may be based on is preferably defined to enable the userequipment to communicate via the communication system.

[0007] The introduction of Third Generation (3G) communication systemswill, in all likelihood, significantly increase the possibilities foraccessing services on the Internet via mobile user equipment (UE) aswell as other types of UE.

[0008] Various user equipment (UE) such as computers (fixed orportable), mobile telephones, personal data assistants or organisers andso on are known to the skilled person and can be used to access theInternet to obtain services. Mobile user equipment, typically referredto as a mobile station (MS), can be defined as a means that is capableof communication via a wireless interface with another device such as abase station of a mobile telecommunication network or any other station.

[0009] The term “service” used above and hereinafter will generally beunderstood to broadly cover any service or goods which a user maydesire, require or be provided with. The term also will generally beunderstood to cover the provision of complimentary services. Inparticular, but not exclusively, the term “service” will be understoodto include Internet protocol multimedia IM services, conferencing,telephony, gaming, rich call, presence, e-commerce and messaging, forexample, instant messaging.

[0010] The 3G Partnership Project (3GPP) is defining a referencearchitecture for the Universal Mobile Telecommunication System (UMTS)core network which will, in all likelihood, provide the users of userequipment (UE) with access to these services. This UMTS core network isdivided into three principal domains. These are the Circuit Switcheddomain, the Packet Switched domain and the Internet Protocol Multimedia(IM) domain.

[0011] The latter of these, the IM domain, typically makes sure thatmultimedia services are adequately managed. The IM domain typicallysupports the Session Initiation Protocol (SIP) as developed by theInternet Engineering Task Force (IETF).

[0012] SIP is an application layer signalling protocol for starting,changing and ending user sessions as well as for sending and receivingtransactions. A session may, for example, be a two-way telephone call ormulti-way conference session or connection between a user and anapplication server (AS). The establishment of these sessions generallyenables a user to be provided with the above-mentioned services. One ofthe most commonly included features of SIP is that the protocoltypically enables personal mobility of a user using mobile UE byproviding the capability to reach a called party (which can be anapplication server AS) or another user equipment via a single locationindependent address.

[0013] A user connected to SIP based communication system may generallycommunicate with various entities of the communication system based onstandardised SIP messages. SIP is typically defined in an InternetEngineering Task Force (IETF) protocol specification by G Rosenberg etal., titled: “SIP: session initiation protocol” RFC 3261, July 2001.This document is herein incorporated by reference in its entirety.

[0014] One version of the third generation standard is “release 5” or“rel5”. This introduces the IP multimedia core network subsystem thathas been developed to use SIP technology as a basis for all IP servicessuch as voice over IP, amongst others. The SIP standard is a rendezvousprotocol which typically may be used to establish media sessions betweena SIP user agent client (UAC) and a SIP user agent server (UAC). To opena session, SIP generally uses the SDP (session description protocol)protocol and it is thus possible to establish a variety of sessions,depending on the used application both for real time services and nonreal time services. The SIP is generally a flexible protocol that can beused to establish different type of sessions. For example, some sessionsmay require a certain precondition to be satisfied. Other sessions mayrequire reliable provisional responses. Other sessions may requireconfirmation of reserved resources. It is also possible to have avariable number of SDP offer/answer exchanges.

[0015] In order to enable charging correlation at the media componentlevel for charging events related to the same SIP session and generatedin different domains (i.e. access network and IM subsystem (IMS)network) for the same SIP session, the access network chargingidentifier identifying the resource reservation carrying a particularmedia flow (e.g. in GPRS (general packet radio service) access the GPRSCharging Identifier and GGSN (gateway GPRS support node) address) ispreferably to be sent and distributed in the IMS network. This accesscharging identifier is typically sent to P-CSCF(PDF) (proxy call sessioncontrol function and policy decision function respectively) via the Gointerface and distributed in IMS in a SIP “UPDATE” message. With thenext version which has been proposed for the 3GPP standard, “release 6”or “rel6” it is possible that for some session set up scenarios anUPDATE message is not sent at all. This generally results in the problemthat the network is unable to distribute the charging identifier betweenthe network elements that require this information.

[0016] In the current proposals for release 5, the UPDATE request istypically sent from the user equipment to the P-CSCF. A confirmation ofthe preconditions are commonly requested in a response when the userequipment finishes a quality of service reservation for both the up linkand down link directions. The calling party generally sends the UPDATErequest to the terminating end point via the signalling path establishedby the INVITE request. The UPDATE request frequently includes in theSDP, the information about the successful quality of servicebi-directional mode, due to the successful bi-directional PDP contextestablished. The SDP generally indicates that the quality of serviceresource reservation for both send and receive mode was successful fromthe terminating end point side.

[0017] With the proposals for release 6, for example, it is possiblethat a session can be established by a simple SIP INVITE/200 OKtransaction or it is possible that the end points involved in thesession set up will not make use of preconditions or not ask forconfirmation of reserved resources. In all of these cases, the UPDATEmessage will typically not be sent and thus distribution of the chargingidentity is generally not possible.

SUMMARY OF THE INVENTION

[0018] It is an aim of certain embodiments of the present invention toaddress the problems discussed previously.

[0019] According to a first embodiment of the present invention, thereis provided a method for supporting a communication session of an userequipment, by means of a communication system that includes at least oneentity between the user equipment and a node with which the userequipment is arranged to establish a session. The method typicallyincludes the step of establishing a session between the user equipmentand the node via the at least one entity, putting the session on hold,reserving resources for the session while the session is on hold, andresuming the session and distributing charging information.

[0020] According to a second embodiment of the invention, there isprovided a method for supporting a communication session of an userequipment, by means of a communication system that includes at least oneentity between the user equipment and a node with which the userequipment is arranged to establish a session. The method typicallyincludes the step of modifying an existing session between the userequipment and the node via the at least one entity, putting the sessionon hold, reserving resources for the modified session while the sessionis on hold, and resuming the session and distributing charginginformation.

[0021] According to another embodiment of the invention, there isprovided a communication system for supporting a communication sessionof an user equipment, the system typically including at least one entitybetween the user equipment and a node with which the user equipment isarranged to establish a session, the system typically being arranged toestablish a session between the user equipment and the node via the atleast one entity, at least one of the node and the user equipment beingarranged to put the session on hold, at least one of the node and theuser equipment being arranged to reserving resources for the sessionwhile the session is on hold, at least one of the node and the userequipment being arranged to resume the session; and at least one entityis typically arranged to distribute charging information.

[0022] According to another embodiment, there is provided acommunication system for supporting a communication session of an userequipment, the system typically including at least one entity betweenthe user equipment and a node with which the user equipment is arrangedto establish a session, the system generally being arranged to modify asession between the user equipment and the node via the at least oneentity, at least one of the node and the user equipment often beingarranged to put the session on hold, at least one of the node and theuser equipment being arranged to reserving resources for the modifiedsession while the session is on hold, at least one of the node and theuser equipment typically being arranged to resume the session and atleast one entity is commonly arranged to distribute charginginformation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] For a better understanding of certain embodiments of the presentinvention and as to how these embodiments may be carried into effect,reference will now be made to the accompanying drawings in which:

[0024]FIG. 1 shows a schematic system in which certain embodiments ofthe present invention may be implemented;

[0025]FIG. 2 shows the signal flow in a first embodiment of theinvention; and

[0026]FIG. 3 shows the signal flow in a second embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

[0027] In this document, SIP messages are indicated in capitals.

[0028] Certain embodiments of the present invention are particularlyapplicable to the release 6 version of 3GPP which will typically allowthe terminals, in other words, the user equipment, to decide forthemselves how to use SIP for communication purposes. It should beappreciated that certain embodiments of the present invention may beapplicable to any other version of the 3GPP standard or indeed any otherstandard.

[0029] Certain embodiments of the present invention are arranged todefine a mechanism which works with the existing SIP specifications toensure the proper working of the charging correlation mechanism in anyscenario where no precondition is used or UPDATE is only used to modifythe already set up session. In other words, if an UPDATE request is notused in the session setup phase before the dialog is confirmed, in otherwords, final response received to the request, certain embodiments ofthe present invention may be used.

[0030] Reference is made to FIG. 1 which shows schematically a system inwhich certain embodiments of the present invention may be implemented.The system typically includes user equipment 2. The user equipment 2 maytake any suitable form and may, for example, be a mobile or fixed entitysuch as a mobile telephone, personal digital assistant (PDA), portablecomputer, laptop computer, fixed computer or any other suitable device.The user equipment 2 is typically arranged to communication with a firstradio access network (RAN) 4 a via a wireless connection. This wirelessconnection may be at any suitable frequency, such as, for example, aradio frequency.

[0031] The first radio access network 4 a generally includes a basestation entity (sometimes referred to as node B). For the purpose ofthis document, the term base station will be used and is intended tocover any suitable entity. The radio access network 4 also typicallyincludes a control element. Depending on the standard, the controlelement may be referred to as a radio network controller (RNC) in thecase of a UMTS system or a base station controller (BSC) in the case ofa GSM system. It is intended that the term controller cover any suchcontrol entity. In some arrangements, the control function is providedseparately from the base station function and a single control entitymay control a number of base stations. In other embodiments of thepresent invention, each base station may incorporate part of the controlfunction.

[0032] The radio access network is typically arranged to communicatewith a core network 6. The core network 6 illustrated in FIG. 1 is apacket switched core network. The first radio access network 4 isgenerally connected to a serving GPRS (general packet radio service)support node SGSN 10. The SGSN 10 is commonly used to switch the packetswitched transactions.

[0033] The SGSN 10 is typically connected to first and second gatewayGPRS support nodes GGSN 12 a and b. These are generally switches at thepoint where the core network 6 is connected to external packet switchednetworks. Incoming and outgoing packet switched connections generallywill go through a GGSN. In the arrangement shown in FIG. 1, the GGSNs 12a and b are shown as being connected to an IM (IP multi-media) subsystem14. Each GGSN 12 is typically connected to a P-CSCF 16 a and b (proxycall session control function) respectively. Each P-CSCF 16 a and bgenerally has a PDF (policy decision function). PDF is commonly part ofthe service based local policy (SBLP) architecture of the IP multimediasubsystem. The policy decision function generally is a logical policydecision element which typically uses IP mechanisms to implement servicebased local policy in the IP bearer layer. The PDF generally makesdecisions in regard to SBLP using policy rules and commonly communicatesthose decisions to the GGSN, which is typically the IP policyenforcement point (PEP). In the arrangement shown in FIG. 1, the PDFs 18a and b respectively are shown as being a logical entity of therespective P-CSCF. However, it should be appreciated that in alternativeembodiments of the present invention, the PDF may be a separate entityor incorporated in any other suitable entity.

[0034] The P-CSCF 16 a and b are generally connected to aninterrogating(I)-CSCF 22. The I-CSCF 22 is typically arranged todetermine the appropriate serving-CSCF (S) 24 for the end user, that is,the called party.

[0035]FIG. 1 also shows an application server AS 23 in the IM network.The GCID may be distributed to the AS in some embodiments of theinvention.

[0036] Also shown in FIG. 1 is a user 30 which typically does notoperate in accordance with the third generation standard and, forexample, may use the SIP protocol. The user 30 is generally connected toa SIP proxy 32 which commonly enables the user agent client to obtainservices via the IM subsystem 14. The SIP proxy 32 is typicallyconnected to the S-CSCF 24. The SIP proxy may be part of an ISP core.The user may be user equipment such as a PC, softphone or the like.

[0037] In certain embodiments of the invention, the core network 6 andthe IMS system 14 may be connected to a CGF (Charging Gateway Function)40 which generally includes a charging collector function CCF. The CCFalternatively may be a separate entity. The CGF 40 is commonly connectedto a billing system 42. The billing system is typically part of theoperator's network. Likewise the CGF is usually part of the operator'snetwork. The CGF and/or the billing system often use a common chargingidentifier that is typically generated in the network (access and IMS)to correlate charging information which then commonly determines howmuch a user is billed for a given session. It should be appreciatedthat, in alternative embodiments of the invention, any other suitablebilling mechanism may be used.

[0038] Also shown in FIG. 1 is a second user equipment 26 which isgenerally connected to a second RAN 4 b. It should be appreciated thatthis is for illustrative purposes and in practice each RAN may bearranged to communicate with a relatively large number of userequipment. The second RAN 4 b is often connected to the SGSN 10.

[0039] Also shown in FIG. 1 is a terminal 43 such as a PC or the likewhich is commonly arranged to be connected to the second P-CSCF 18 b viaanother access network 44 which may be in accord with any suitableaccess technology.

[0040] In certain embodiments of the present invention, the SIP useragent client UAC is the calling party which at least in the two examplesshown may be the user equipment 2 and the user equipment 30. The SIPuser agent server UAS is commonly the called party which, at least inthe examples shown, may be the user equipment 26 and the user equipment2. It should be appreciated that this is by way of example only and anyof the terminals or user equipment may be the called party and thecalling party, respectively.

[0041] In certain embodiments of the invention, the GCID (GPRS chargingidentifier) is typically sent from the GGSN to the PDF functionality. Ifthe PDF functionality is separate from the P-CSCF, the GCID may also besent to the P-CSCF. The messages may be sent over the Go interface, thatis generally the interface between the GGSN and the P-CSCF, typicallyusing COPS (Common Open Policy Service) protocol messages. COPS isgenerally the protocol used for the Go interface. The GCID is oftendistributed in SIP signalling to other IMS functions such as, but notlimited to, the S-CSCF, the application server and the I-CSCF.

[0042] The GCID is commonly generated by the GGSN for a GPRS PDPcontext. There is typically a one to one relationship between the GCIDand the PDP context. If GPRS is generally used to access the IMS, theGCID is used together with the GGSN address as the access part of thecharging correlation vector that typically includes an access part andan IMS part, which is generally the IMS charging identifier. Thecharging vector is described in more detail hereinafter.

[0043] It should be appreciated that embodiments of the presentinvention may be used with access technologies other than GPRS. Forexample, certain embodiments of the invention are particularlyapplicable where the PDF function and the Go interface are used, that iswhere SBLP is commonly used at least for charging correlation.

[0044] If the terminal, in other words, the user equipment, does not usepreconditions or 100 REL (SIP preconditions) then it is not possible todistribute the GCID. In this scenario, the terminal will typically putthe session on hold during the first SDP (session description protocol)offer/answer exchange. After reserving the resources for the session,the terminal will generally resume the session with a re-INVITE messagewhich may then distribute the GCID from the P-CSCF to other IMSfunctions. The GCID is commonly included in a P-charging-vector, whichis described in more detail hereinafter. In particular, the P-CSCF willoften put the GCID information into the P-charging-vector header in there-INVITE request which typically resumes the media previously put onhold.

[0045] In the alternative, if the terminal modifies the existing sessionby adding a media component or changing the previously used codec, thereis generally no opportunity to carry the GCID to the S-CSCF or otherfunctions in the IMS. Thus, in this case and according to certainembodiments of the present invention, the terminal typically puts thenew media on hold and generally resumes the media with a re-INVITEmessage once the resources have been successfully reserved. There-INVITE message thus often distributes the GCID in the IMS network.

[0046] Certain embodiments of the present invention may be used in IMSnetwork with whatever access network is used. According to many of theseembodiments, the Go interface is implemented at least for chargingcorrelation.

[0047] Reference is now made to FIG. 2 which shows the signallingcommonly used in a first embodiment of the present invention. Thoseelements which are the same as or analogous to those shown in FIG. 1 arereferred to using the same reference numbers. It should be appreciatedthat some elements, for example the I-CSCF, which would generally bepresent in practice have been omitted for clarity. This embodiment ofthe invention shows an example where the calling party is a non thirdgeneration entity.

[0048] In step S1, the UAC or user equipment 30 commonly sends an INVITEmessage to a non-3GPP SIP proxy 32. The SIP proxy 32 generally sends theINVITE message in step S2 to the S-CSCF 24. The S-CSCF 24 typicallysends the INVITE message in step S3 to the first P-CSCF 16a, and morespecifically, according to certain embodiments, to do PDF functionthereof. The first P-CSCF 16 a generally forwards the INVITE message instep S4 to the user agent server or user equipment 2. The user agentserver 2 typically causes the media streams to be inactive in step S5.

[0049] The user agent server 2 generally sends a message to the firstP-CSCF 16 a in step S6 may be a 200 OK message and commonly indicates inthe SDP that the session is inactive. This message is typicallyforwarded by the first P-CSCF 16 a to the S-CSCF 24 in step S7. In stepS8, the message is generally forwarded by the S-CSCF 24 to the SIP proxy32. In step S9, the message is commonly forwarded by the SIP proxy 32 tothe user agent client 30.

[0050] In step S10, the user agent client 30 typcially sends anacknowledgement ACK that it has received the message. Thisacknowledgement commonly includes the SDP indicating inactive session.This is generally sent to the SIP proxy 32. In step S11, the SIP proxy32 typically forwards the message to the S-CSCF 24. This message may beforwarded in turn by the S-CSCF 24 to the first P-CSCF 16 a in step S12.In S13, the messages may be forwarded by the first P-CSCF 16 a to theuser agent server 2. In step S14, the user agent server 2, inconjunction with first GGSN 12 a, typically reserve resources. In stepS15, once the resources have been reserved, the media streams may be setto be active by the user agent server 2. Step S15 may take place at thesame time as step S16. In step S16, there may be interactions betweenthe GGSN 12 a and P-CSCF 16 a via the Go interface. In this step ICID(IMS Charging Identifier) and GCID information may be exchanged. TheICID may be used for session level correlation while the GCID typicallyis used for media component level correlation. GCID identifies theaccess charging information related to a particular media componentassuming that session/media are not multiplexed in the same PDP Context(3GPP Rel 5).

[0051] In step S17, the user agent server 26 may send a re-INVITEmessage with the SDP indicating active session, in other words, themedias attributes may be set to sendrecv. a=sendrecv for all the mediasthat need to be active in the session. This message is typicallyforwarded by the first P-CSCF 16 a to the S-CSCF 24. However, the firstP-CSCF 16 a may also include the P-charging vector with the GCIDinformation. The S-CSCF 24 generally forwards the INVITE message (withor without the P-charging vector) in step S19. In step S20, the messageis commonly sent from the SIP proxy 32 to the UAC 30.

[0052] Reference is made to FIG. 3 which shows a second embodiment ofthe present invention. This embodiment illustrates a representativesignal flow for an example of a session established between 3GPP useragents without any preconditions. According to this embodiment, there isa first 3GPP user application client, which may be the user equipment 2.This is typically associated with the first GGSN 12 a and the firstP-CSCF 16 a with a PDF functionality. The user application agent serveror user equipment 26 is generally associated with the second GGSN 12 band a second P-SCSF 16 b. The two P-CSCFs are often communicating via acommon S-CSCF 24. However, in some embodiments of the present invention,more than one S-CSCF may be provided and indeed there are other entitieswhich have been omitted for clarity.

[0053] In step T1, the user agent client 2 commonly sets the mediastreams to be inactive. In step T2, the user agent client 2 typicallysends an INVITE message with SDP indicating the media streams areinactive to the first P-CSCF 16 a. The first P-CSCF 16 a generallyforwards the message in step T3 to the S-CSCF 24. The S-CSCF 24typically forwards the message in step T4 to the second P-CSCF 16 bwhich, in turn, generally forwards that message in step T5 to the useragent server 26.

[0054] In step T6, the user agent server 26 commonly sends a 200 OKacknowledgment with the SDP indicating an inactive session to the secondP-CSCF 16 b. In step T7 the message is typically forwarded by the secondP-CSCF 16 b to the S-CSCF 24 which, in turn, generally forwards thatmessage to the first P-CSCF 16 a in step T8. The first P-CSCF 16 acommonly forwards the message in step T9 to the user agent client 2.

[0055] In step T10, the user agent client 2 typically sends anacknowledgement message ACK to the first P-CSCF 16 a. Thisacknowledgement is generally forwarded by the first P-CSCF 16 a to theS-CSCF 24 in step T11 and by the S-CSCF 24 to the second P-CSCF 16 b instep T12. The acknowledgment may be forwarded by the second P-CSCF 16 bin step T13 to the user agent server 26.

[0056] In step T14, resource reservation is commonly carried out betweenthe user agent server 26 and the second GGSN 12 b. Step T16 may takeplace at the same time as step T14 and resources may be reserved betweenthe user agent client 2 and the first GGSN 12 a. In step T15, there istypically interaction between the second GGSN 12 b and the second P-CSCF16 b on the Go interface involving the ICID and the GCID. This is oftenas described in relation to FIG. 2. Step T17 is generally similar tostep T15 but between the first GGSN 12 a and the first P-CSCF 16 a.Steps T15 and T17 may take place at the same time. In step T18, the useragent client 2 typically sets the media streams to be active.

[0057] The user agent client 2 then usually sends an INVITE message withSDP indicating active media streams, (in other words, the mediasattributes are typically set to sendrecv. a=sendrecv for all the mediasthat need to be active in the session) information in step T19 to thefirst P-CSCF 16 a.

[0058] In step T20, the P-CSCF 16 a commonly adds in theP-charging-vector including the GCID. In step T21, the INVITE messagemay be forwarded by the S-CSCF 24 to the second P-CSCF 16 b which inturn generally forwards that message in step T22 to the user agentserver 26. The user agent server 26 typically sends an acknowledgementmessage 200 OK with the SDP containing an a=sendrecv information. Thesecond P-CSCF 16 b normally sends a message in step T24 to the S-CSCF 24along with the P-charging-vector with the GCID information. In step T25,the S-CSCF 24 usually forwards the message without theP-charging-vector, to the first P-CSCF 16 a which, in turn, commonlyforwards that message to the user agent client 2 in step T26.

[0059] In one alternative modification to the arrangement shown in thefirst embodiment, the initial INVITE messages (steps S1 to S4) mayinclude SDP with a=sendrcv information, as in steps T1 to T5 of thesecond embodiment. Likewise, steps S10 to S13 may be modified in such ascenario to have the same form as shown in steps T10 to T13 of thesecond embodiment, that is, not to include the SDP information.Conversely, steps T1 to T5 may be modified so that the INVITE messagedoes not include the SDP information as in steps S1 to S4 of the firstembodiment. Likewise, the acknowledgement message sent in steps T10 toT13 may have the SDP media stream inactive information.

[0060] The table below shows representative P-charging-vector in moredetail. This is defined in the 3GPP specification number TS 24.229 andTS 24.228 which is hereby incorporated in its entirety by reference.access-network-charging-info = (gprs-charging-info / generic-param)gprs-charging-info = ggsn *(SEMI pdp-info) [SEMI extension-param] ggsn =“ggsn” EQUAL gen-value pdp-info = pdp-sig SEMI gcid SEMI auth-token*(SEMI flow-id) pdp-sig = “pdp-sig” EQUAL (“yes” / “no”) gcid = “gcid”EQUAL gen-value auth-token = “auth-token” EQUAL gen-value flow-id =“flow-id” EQUAL gen-value extension-param = token [EQUAL (token |quoted-string)]

[0061] The P-charging-vector header field typically has the fieldsdescribed in RFC 3455 of the IETF which is hereby incorporated in itsentirety by reference.

[0062] The access network charging info parameter is usually anincidence of a generic parameter from the current charge parametercomponent of the P-charging-vector header. The access network charginginfo parameter normally includes alternative definitions for differentaccess networks. In this example, GPRS may be the supported accessnetwork as indicated in the GPRS-charging-parameter. In otherembodiments of the invention, other access networks may be supported.For GPRS there are generally the following components to track; GGSNaddress and one or more PDP contexts (PDP-info parameter), an associatedGPRS charging identifier (GCID parameter), a media authorisation token(or-token parameter) and one or more flow identifiers (flow-idparameter) that typically identify associated m-lines within the SDPfrom the SIP signalling. These parameters are usually transferred fromGGSN to the P-CSCF (PDF) over the Go interface.

[0063] It should be appreciated that embodiments of the presentinvention can be used for on-line charging or off-line charging.

[0064] It is noted herein that while the above described areexemplifying embodiments of the invention, there are several variationsand modifications which may be made to the disclosed solution withoutdeparting from the scope of the present invention as defined in theappended claims.

We claim:
 1. A method for supporting a communication session of userequipment, by a communication system comprising at least one entitybetween said user equipment and a node with which the user equipment isarranged to establish a session, the method comprising the steps of: a)establishing a session between the user equipment and the node via saidat least one entity; b) putting the session on hold; c) reservingresources for said session while said session is on hold; d) resumingsaid session; and e) distributing charging information.
 2. The method asclaimed in claim 1, further comprising the step of determining ifcharging information is provided during the establishment of saidsession and carrying out steps b) to d) only when it has been determinedthat the charging information has not been provided.
 3. A method forsupporting a communication session of user equipment, by means of acommunication system comprising at least one entity between said userequipment and a node with which the user equipment is arranged toestablish a session, the method comprising the steps of: a) modifying anexisting session between the user equipment and the node via said atleast one entity; b) putting the session on hold; c) reserving resourcesfor the modified session while said session is on hold; and d) resumingsaid session and distributing charging information.
 4. The method asclaimed in claim 3, further comprising the step of determining ifcharging information is provided during the modifying of said sessionand carrying out steps b) to d) only when it has been determined thatthe charging information has not been provided
 5. The method as claimedin claim 1, wherein the establishing step comprises using SIP for saidsession.
 6. The method as claimed in claim 1, wherein the establishingstep comprises operating at least part of said communication system inaccordance with UMTS standard.
 7. The method as claimed in claim 1,wherein the distributing step comprises distributing said charginginformation comprising a charging identifier.
 8. The method as claimedin claim 7, wherein the distributing step comprises distributing saidcharging information and wherein said charging identifier comprises atleast one of a GCID and an ICID.
 9. The method as claimed claim 1,wherein the distributing step comprises distributing the charginginformation provided in a charging vector.
 10. The method as claimed inclaim 9, wherein the distributing step comprises distributing thecharging information in a charging vector and wherein said chargingvector comprises a P-charging-vector.
 11. The method as claimed in claim1, wherein the establishing step comprises establishing a sessionwherein said at least one entity comprises a GGSN.
 12. The method asclaimed in claim 1, wherein the establishing step comprises establishinga session wherein said at least one entity comprises a P-CSCF.
 13. Themethod as claimed in claim 1, wherein the establishing step comprisesestablishing a session wherein said at least one entity comprises a PDFfunction.
 14. A method as claimed in claim 11, wherein the establishingstep comprises establishing a session wherein said at least one entitycomprises a P-CSCF, the method further comprising the step of sendingthe charging information from the GGSN to the P-CSCF.
 15. The method asclaimed in claim 11, wherein the establishing step comprisesestablishing a session wherein said at least one entity comprises a PDFfunction, the method comprising the step of sending the charginginformation from the GGSN to the TDF.
 16. The method as claimed in claim14, wherein the establishing step comprises establishing a sessionwherein said charging information is sent from the GGSN to the P-CSCF ina COPS message.
 17. The method as claimed in claim 15, wherein theestablishing step comprises establishing a session wherein said charginginformation is sent from the GGSN to the PDF in a COPS message
 18. Themethod as claimed in claim 1, wherein the establishing step comprisesestablishing a session wherein said node comprises a user agent server.19. The method claim as claimed in claim 5, wherein the establishingstep comprises establishing a session wherein said charging informationis sent in an INVITE message.
 20. The method as claimed in claim 1,wherein the establishing step comprises establishing a session whereinsaid node comprises user equipment.
 21. A communication system forsupporting a communication session of an user equipment, said systemcomprising at least one entity between said user equipment and a nodewith which the user equipment is arranged to establish a session, thesystem being arranged to establish a session between the user equipmentand the node via said at least one entity, at least one of said node andsaid user equipment being arranged to put the session on hold, at leastone of said node and said user equipment being arranged to reservingresources for said session while said session is on hold, at least oneof said node and said user equipment being arranged to resume saidsession; and at least one entity being arranged to distribute charginginformation.
 22. A communication system for supporting a communicationsession of an user equipment, said system comprising at least one entitybetween said user equipment and a node with which the user equipment isarranged to establish a session, the system being arranged to modify asession between the user equipment and the node via said at least oneentity, at least one of said node and said user equipment being arrangedto put the session on hold, at least one of said node and said userequipment being arranged to reserving resources for said modifiedsession while said session is on hold, at least one of said node andsaid user equipment being arranged to resume said session and at leastone entity being arranged to distribute charging information.
 23. Acommunication system comprising at least one entity between userequipment and a node with which the user equipment is arranged toestablish a session, the system comprising: establishing means forestablishing a session between the user equipment and the node via saidat least one entity; placement means for putting the session on hold;reserving means for reserving resources for said session while saidsession is on hold; and resuming means for resuming said session and fordistributing charging information.
 24. A communication system comprisingat least one entity between user equipment and a node with which theuser equipment is arranged to establish a session, the systemcomprising: modifying means for modifying an existing session betweenthe user equipment and the node via said at least one entity; placementmeans for putting the session on hold; first reserving means forreserving resources for the modified session while said session is onhold; second reserving means for reserving resources for the modifiedsession while said session is on hold; and resuming means for resumingsaid session and distributing charging information.